Congress will return to Washington this week to confront a series of highly charged partisan issues as a deadline for extending government funding approaches, raising the specter of a December government shutdown.

Leaders of both parties have publicly played down the possibility of a showdown next month. Funding expires on Dec. 8, and both sides have floated the possibility of a short-term stopgap to push negotiations until just before Christmas.

“There shouldn’t be any discussion about shutting down the government. We can make this thing work. We just need to get people at the table, negotiate it,” Sen. John Thune (S.D.), the third-ranking Republican senator, said on “Fox News Sunday.”

But informal talks have been abortive, and bitter partisan divides over spending, health care and immigration threaten to set up an impasse.

The tone could be set quickly. Congressional leaders of both parties are set to meet Tuesday with President Trump at the White House in a summit that could smooth the path for the month ahead — or inflame simmering fights.

President Trump meets with Senate Majority Leader Mitch McConnell (R-Ky.) and House Speaker Paul D. Ryan (R-Wis.) at the White House in March. Democratic leaders will join the three for a summit Tuesday. (Bill O’Leary/The Washington Post)

Trump has not indicated whether this time he will be as amenable. Multiple aides in both parties cautioned that the meeting might not yield an agreement — partly because key issues bedeviling the leaders remain unresolved and also because Republicans want to keep the focus this week on their sweeping tax bill.

While Republicans try to wrap up their tax effort, they must negotiate with Democrats on the litany of other governing items. The first step toward a resolution will be reaching an agreement on government spending levels for 2018 and perhaps beyond, lifting caps imposed under a bipartisan 2011 budget deal.

“I just say, be ready for a potentially wild month in December,” said Rep. Charlie Dent (R-Pa.), a senior member of the House Appropriations Committee who for months has pushed GOP leaders to reach a spending accord with Democrats. “This is going to get a bit complicated.”

Under current law, Congress may appropriate no more than $549 billion for defense programs and $516 billion for nondefense programs next year, a cut from current levels.

But the Trump administration and defense hawks want to boost defense spending to more than $600 billion, and Democrats are demanding a dollar-for-dollar increase in nondefense spending. Because House Republicans have needed Democrats to help pass spending bills in recent years amid opposition from fiscal conservatives and because Senate Democrats can filibuster any spending bill, party leaders have leverage to force a deal.

[House passes nearly $700 billion defense authorization bill]

“We’re going to need their help,” Dent said of Democrats. “And the question for the Democrats is: Are they going to play ball with us?”

Talks before the Thanksgiving holiday focused on raising spending levels somewhere between $180 billion and $200 billion over the next two fiscal years combined but went nowhere, according to multiple people familiar with the negotiations. Aides from both parties warned that if a spending accord is not reached this week, hopes for the passage of a broad appropriations bill before Christmas would be dim.

The GOP tax bill, which is being considered under special procedures that do not require bipartisan cooperation, has made some Democrats increasingly resistant to collaborating with Republicans in any sense.

“The decisions made during the next month will affect Americans’ economic well-being for the next decade,” Sen. Amy Klobuchar (D-Minn.) said Sunday. “Our job is to break through all the tweets and the noise and focus on the economics at hand.”

Aside from the basic task of keeping the government open, lawmakers also are pushing to deliver tens of billions of dollars in additional federal aid to disaster victims across the country before the year ends, including those affected by hurricanes Harvey, Irma and Maria, as well as by Western wildfires. The White House requested another $44 billion in aid this month and asked that the increased spending be offset by unrelated spending cuts, a proposal that quickly earned bipartisan criticism.

Complicating the passage of any spending deal are the highly charged politics of health care and immigration.

Democrats have pushed for the passage of bipartisan legislation drafted in the Senate that would help stabilize the market for individual insurance coverage established under the 2009 Affordable Care Act by appropriating funds that allow insurers to reduce out-of-pocket costs for low-income Americans. Trump canceled the payments, which had previously been made absent congressional appropriation, in October.

But conservative Republicans have opposed any attempt to shore up the ACA, and the GOP tax bill could eliminate a core provision of the law: the tax penalty meant to compel Americans to secure insurance coverage. Moderate Republican senators Susan Collins (Maine) and Lisa Murkowski (Alaska) have said they would like to see the stabilization bill pass alongside any repeal of the ACA mandate, but Schumer has said Democrats would not support passing the stabilization bill under those circumstances.